This invention relates to polyurethanes and, more particularly, to novel haloalkyl polyphosphates capable of imparting long term, flame retardant durability to such polyurethanes.
Considerable effort has been made to provide polyurethane foams with satisfactory flame retardancy. In general, a wide variety of organophosphorus compounds, typically containing chlorine and/or bromine, have been proposed and utilized. These compounds are conventionally designated as being of either the additive type or the active type. The latter type possess functionality which allows chemical incorporation into the resulting polyurethane.
The problem of providing adequate flame retardancy is particularly acute when flexible urethane foams are involved. It is thus generally accepted that achievement of adequate flame retardant durability in flexible urethane foams at acceptable levels of the flame retardant (i.e. - the ability to maintain an adequate level of flame retardancy after exposure to heat aging conditions) requires utilizing flame retardants of the reactive type.
For example, two of the commercially used material of the additive type have the following structural formulas: ##STR1## These impart durability but achieve this only by use of relatively high levels. In addition to the associated economic penalty, relatively high levels of flame retardants often adversely affect certain physical properties of the foams such as, for example, tensile and tear strength and compression sets.
A further approach utilizes flame retardant materials which are described as haloethylterminated phosphoric acid ester polymers having repeating phosphate ester groups interconnected with ethylene ester groups. These compounds are formed by heating a tris (2-haloethyl) phosphate or a mixture of 2-haloethyl phosphoric acid ester compounds containing at least 50% by weight of tris (2-haloethyl) phosphate and up to 50% by weight of at least one other phosphoric acid ester having at least one 2-haloethyl substituent to a temperature within the range of 170.degree. C. to 220.degree. C. in the presence of a basic catalyst for a period of time sufficient to generate reaction by-product ethylene dihalide in an amount of from 0.5 mole to 0.9 mole per mole of the 2-haloethyl phosphorous reactant.
In use, such compounds have been principally employed as flame retardants for textiles. No substantial acceptance in polyurethane foam formulations have been achieved. Such compounds are typically insoluble in various conventional polyols used in flexible foams, and this lack of compatibility can cause inconsistent flame retardant and foam properties, particularly when introduced with a stream including the polyol. In addition, such compounds require relatively high levels to achieve adequate flame retardant durability.
It is accordingly an object of the present invention to provide novel organophosphates capable of imparting improved flame retardancy to polyurethanes. A related and more specific object lies in the provision of novel organophosphates which impart improved flame retardancy to flexible polyurethane foams.
A further object provides flame retardants which impart, in terms of flame retardance, long term durability for flexible polyurethane foams.
Yet another object of this invention is to provide novel organophosphates having superior compatibility with flexible polyurethane foam formulations. A more specific and related object provides organophosphates which are soluble in polyols typically used for forming flexible urethane foams.
Yet another object provides novel organophosphates which may be economically manufactured.
Another object lies in the provision of organophosphates characterized by relatively high flame retardant efficiency.
Other objects and advantages of the present invention will become apparent from the following detailed description.